What Causes Neck And Arm Pain?

I am also suffering from neck and arm pain on the left side i have had an mri and xrays done they say its the c4 c5 c7 if i remember correctly i recnetly went to a workers comp dr and he is saying that there is no way this is a work related injury can this be true? i have been delaing with this pain for a lil over a yr now>